This invention relates to a pneumatic power tool of the type having a housing with a pistol type handle, a motor in the housing, a pressure air inlet passage and an exhaust air passage extending substantially in parallel to each other through the handle, and a manually operable throttle valve located in the air inlet passage.
In this type of power tool, as for example in the tool disclosed in GB 2 098 528, it is difficult to satisfy the demand for good heat insulation in combination with an acceptable grip size of the handle.
In a tool of the above type, the handle is formed in a heat conducting light metal alloy, and since the exhaust air passing through the handle is very cold due to previous expansion in the motor, the outer surface of the handle becomes uncomfortably cold for the operator.
In order to solve this cold problem, an insulating layer of a suitable material sometimes been applied on the outside of the handle. This adds to the grip size of the handle and makes the handling of the tool not only uncomfortable and tiresome but in some cases unsafe.
Another problem with the above type of power tool is that the grip size of the handle is not variable. This means that a comfortable handling of the tool is only available to those operators who have a certain hand size, whereas the handle is too thick for persons with smaller hands, like many female operators, but too slim for persons with big hands.
A solution to chis problem and also to the cold problem is shown in EP-A-481 947. In this publication there is described a penumatic power tool with a pistol type handle having a grip element which is easily excangeable for alternative grip elements of different sizes to suit different operators. The cold problem is solved because exhaust air does not at all pass through the handle. Instead, this known tool has a specially designed housing for communicating inlet air as well as exhaust air between a top location on the housing and the motor.
Apart from the fact that this known tool housing is more complicated and more expensive, the inlet and exhaust air passages are separated from the handle. This means that the most common and in most cases the most suitable air conduit connection and exhaust air outlet at the outer end of the handle is not possible in this prior art tool.